The present invention pertains to a bumper system for use on an automatic guided vehicle (AGV) and in particular to such a system capable of stopping the vehicle when an object is struck.
Briefly, AGV's are driverless vehicles which transport goods and materials from one location to another. Generally, AGV's are controlled by an on-board computer and follow a cable embedded in the floor. Ideally, the AGV's path is kept clear of any obstacles. Nevertheless, people, products or other materials are occasionally in the AGV's path. The AGV should therefore preferably have the capacity to sense such obstructions and come to a stop.
Safety bumper systems with the capacity to stop the movement of an AGV are commonly used. One such system involves a bumper comprised of two superimposed electrically conductive strips. In the normal driving position, the strips are spaced apart with a small gap defined therebetween. Upon striking an object the strips contact each other and function as a switch to stop the vehicle. However, an uneven driving motion or a rough surface can cause the strips to be jostled and thereby contact one another and stop the vehicle without the imposition of an obstruction. Further, the conductive bumper strips are generally composed of metal and are therefore susceptible to being dented or deformed, detracting from performance and appearance.
Another system has involved optical sensors designed to detect movement of the bumper. In particular, a reflector is generally positioned on the bumper to cooperate with at least one sensor strategically mounted on the AGV. Examples of these arrangements are illustrated in U.S. Pat. No. 4,802,548 to Kausch, U.S. Pat. No. 4,730,690 to McNutt et al., and U.S. Pat. No. 3,664,701 to Kondur. In certain situations, however, the reflector can remain within the beam of the sensor even though an obstruction had been struck. Additionally, reflectors have often been placed on the most remote portions of the bumpers where swaying can become a significant factor. Swaying in such arrangements can cause the reflector to stop the AGV without the bumper striking an obstruction. Further, those systems are relatively expensive.
Safety bumpers have also been designed to cooperate with switches engaging movable links and the like which are adapted to move with the bumper when an object is contacted. Examples of such constructions are illustrated in U.S. Pat. No. 4,635,982 to Feldmann et al., U.S. Pat. No. 4,288,121 to Wiechert, U.S. Pat. No. 4,137,984 to Jennings et al., and U.S. Pat. No. 3,599,744 to Satterfield et al. However, switch arrangements have often involved elaborate mechanisms and been costly to manufacture.